Tartare sauce: place all the ingredients for the tartare sauce into a bowl and mix well. Set aside.
Prawn Patties: blend with a food processor or finely chop half of your prawns into a paste. Finely chop the other half of your prawns and them together into a bowl. Add the cornstarch, sesame oil, salt and pepper and mix vigorously into a sticky paste.
Breading: set up your breading station - flour, beaten eggs and panko breadcrumbs. Scoop half of your prawn mixture into your lightly oiled hands and roll the mixture into a ball. Slam the ball between the hands to remove any air bubbles and flatten the ball into a round patty. Coat the patty into plain flour, followed by egg and lastly panko breadcrumbs. Repeat with the remaining prawn mixture and set aside.
Frying: bring a pot of neutral/vegetable oil to 180C/250F. Carefully place the patties into the oil and cook for 4-5 minutes, flipping halfway. Remove from oil and drain on a cooling rack.
Assemble: cut off the crusts from the sandwich slices. Place a handful of shredded cabbage onto 1 slice, followed by a drizzle of the homemade tartare sauce, prawn patty and lastly the second slice of bread. Cut the sandwich in half to reveal the cross section and enjoy!